tcp: avoid indirect call in tcp_new_space()

For tcp sockets, sk->sk_write_space is most probably sk_stream_write_space().

Other sk->sk_write_space() calls in TCP are slow path and do not deserve
any change.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -5383,7 +5383,7 @@ static void tcp_new_space(struct sock *sk)
 		tp->snd_cwnd_stamp = tcp_jiffies32;
 	}
 
-	sk->sk_write_space(sk);
+	INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk);
 }
 
 static void tcp_check_space(struct sock *sk)